The basic objective of this work is to characterize the transepithelial transport of water and ions across the mammalian airway. These studies will be done in both the trachea and bronchi of the ferret and white rabbit so that regional differences in airway transport can be discerned. Stationary and dynamic perfusion techniques will be used for water flux studies, while electrophysiologic measurements will be made on both tubular airways and flat surfaces (Ussing technique). These studies will characterize the nature and regulation of water and ion transport in the mammalian airways and elucidate differences not only between regions but also between epithelial membranes with and without submucosal glands.